One approach to processing tar sands that has been extensively investigated is the use of alkaline reagents such as alkali metal silicates, phosphates, carbonates or hydroxides as a bitumen separation reagent at elevated temperature or in presence of a solvent. Fyleman (U.S. Pat. No. 1,615,121) treats tar sand with dilute aqueous solution of alkali carbonate, hydroxide or silicate heated from 60.degree. to 80.degree. C. Clark (U.S. Pat. No. 1,791,797) adds a polyvalent salt such as a calcium or aluminum salt to the alkaline reagent as a coagulant. U.S.S.R. Pat. No. 2,924,772 mixes an aqueous suspension of tar sands with diesel alkaline waste, separates and adds sodium silicate to the lower phase, combines it with the upper phase to form a second upper phase. Willard, Sr. (U.S. Pat. No. 3,951,778) also discloses use of a hot (40.degree. C.-90.degree. C.) aqueous silicate solution containing calcium and magnesium which additionally contains a micelle forming surfactant such as metal soap. Fischer (U.S. Pat. No. 2,903,407) stored an aqueous suspension of tar sand at ambient temperature (60.degree. F.-160.degree. F.) before adding hydrocarbon solvent and mixing at elevated temperature. Bauer et al (U.S. Pat. No. 2,453,060) adds sodium silicate or carbonate to an aqueous suspension of tar sands prior to hot pulping; solvent is then added. Stegmemeir et al (U.S. Pat. No. 2,924,565), Vaell et al (U.S. Pat. No. 2,924,566), Sherbourne (U.S. Pat. No. 2,921,010), Fischer (U.S. Pat. No. 2,957,818), Kelly (U.S. Pat. No. 2,980,600) and Sheffel et al (U.S. Pat. No. 3,075,913) are all commonly assigned and relate to improvements in a process in which bitumen is separated from tar sand by pulping a warm silicate-solvent solution in a rotary kiln pulper. Richard (U.S. Pat. No. 3,330,757) and Cannevari (U.S. Pat. No. 3,331,768) use an aqueous treating solution containing a transfer agent such as a phosphate, a silicate and a chelating agent and/or a demulsifier to separate bitumen from tar sand. Floyd et al (U.S. Pat. No. 3,401,110) disclose the hot water process for treating tar sands and teaches the cold water process requires the use of a light hydrocarbon solvent in order to achieve a reasonably good separation.
Most processes employ some form of mixing during the separation step. U.S. Pat. Nos. 4,054,505 and 4,054,506 disclose sonicating a dispersion of tar sand in solvent having sufficient strength to break apart and to remove bitumen from the surfaces of the sand grains.
All of these processes require use of heat and/or solvent in order to separate bitumen from tar sand. In our earlier experiments it was surprisingly discovered that bitumen can be separated from tar sands at ambient temperature using dilute aqueous solution of inorganic bases such as sodium silicates by subjecting the suspension to vigorous mixing, for example, in the vortex of a mixer imparting turbulence and high shear to the suspension. A portion of the bitumen was recovered after several days of treatment. A small amount of oil with a high ash content was recovered from the top of the suspension.